Session 4 - Congenital heart defects & cellular and molecular events in CVS Flashcards
What are the 2 types of congenital malformation of the heart & great vessels?
Acyanotic & cyanotic
Describe the movement of blood in terms of concentration gradient
Travels down the concentration gradient (high to low)
Left to Right
What are acyanotic defects?
blood in the systemic circulation is fully saturated with O2 so pO2 is maintained
What are the 6 types of acyanotic defects?
- Atrial septal defect (ASD)
- Ventricular septal defect (VSD)
- Patent foramen ovale (PFO)
- Patent Ductus Arteriosus (PDA)
- Coarctation of the aorta
- Atrioventricular septal defect
What is an atrial septal defect (ASD)?
- Opening in septum/wall between 2 atria
- Blood in LA able to flow to RA so no mixing of deoxygenated blood with the oxygenated blood being pumped around the systemic circulation (body receives O2 - acyanotic)
What is ASD mostly caused by?
deformation of the septum primum or septum secundum
What is the problem associated with atrial septal defect (ASD)?
- Blood is able to move from LA to RA due to an opening between atria
- Increased blood in RA => RV overload => more blood pumped around pulmonary system
What is a ventricular septal defect (VSD)?
- Abnormal opening in the interventricular septum
- Blood in LV flows into RV
What is VSD caused by?
caused by the membranous portion of the septum no developing properly meaning primary interventricular foramen remains open
What is a patent ductus arteriosus (PDA)?
Ductus arteriosus connecting right pulmonary artery to arch of aorta remains open (supposed to close when baby takes a first breath)
What occurs in a patent ductus arteriosus?
Allows blood under high pressure in aorta to flow into pulmonary artery
=> higher volume of blood in pulmonary artery
=> higher afterload for RV
=> RS failure
What happens if a patent ductus arteriosus is left untreated?
Congestive heart failure due to increased return to LS of heart
How are patent ductus arteriosus acyanotic?
blood reaching systemic circulation is fully saturated with O2 from lungs
What is the coarctation of the aorta?
narrowing of aortic lumen in former ductus arteriosus area
How does coarctation of the aorta lead to LV hypertrophy?
Narrowing of the aorta increases afterload of LV causing LV hypertrophy
Which parts of the body are compromised in the coarctation of the aorta? What are the effects?
Reduced blood flow to the lower part of the body causes weak pulses & cramping in legs
Why is the blood supply to the head & upper limbs not compromised in coarctation of the aorta?
the regions are proximal to the coarctation
What are the risks of coarctation of the aorta?
increased pressure due to narrowing leads to increased risk of aneurysms of aortic arch & aortic root dilation which can lead to aortic valve regurgitation
What is atrioventricular septal defect?
hole in middle of heart with one common atrioventricular valve instead of mitral and pulmonary valve
What is an atrioventricular septal defect caused by?
failure of endocardial cushions to develop properly
In which disease is the atrioventricular septal defect common?
Down’s syndrome
What is a cyanotic defect?
blood in systemic circulation is NOT saturated with O2 so pO2 is low
What are the 6 types of cyanotic defects?
- Tetralogy of Fallot
- Tricuspid atresia
- Pulmonary atresia
- Hypoplastic Left Heart
- Univentricular Heart
- Transposition of the Great Arteries
What is Tetralogy of Fallot?
Group of 4 lesions occurring together as a result of a single development defect
Name & describe the 4 lesions of Tetralogy of Fallot?
- Pulmonary stenosis: pulmonary artery or valve is narrowed => less can blood enter
- Overriding aorta: aorta is situated next to the VSD rather than over LV so most of the blood in the heart flows through it [VSD]
- VSD: allows blood from RV [which cannot be pumped through stenosed pulmonary artery/valve] to move into LV & is pumped around body via aorta
- Hypertrophy of RV: caused by attempts to generate more force to pump blood through stenosis into pulmonary artery
What is tricuspid atresia?
Tricuspid valve fails to form, blood cannot flow from RA to RV (no opening)
How does blood continue to flow into pulmonary circulation in tricuspid atresia?
ASD & VSD are present
What is pulmonary atresia?
Pulmonary valve fails to form, blood cannot flow from RV to pulmonary artery & leave heart – only way to leave RS is through a defect
How does blood continue to flow into pulmonary circulation in pulmonary atresia?
Patent ductus arteriosus allows blood into pulmonary circulation as blood in aorta can flow into pulmonary artery
What is a hypoplastic left heart?
Mitral or aortic valves are stenosed in utero = less blood flows in LV => LV is underdeveloped
How does blood continue to flow into pulmonary circulation in hypoplastic left heart?
- ASD allows blood to flow into RS of heart & pumped into pulmonary artery
- PDA allows blood to enter aorta from left pulmonary artery
What is univentricular heart?
- Ventricular septum doesn’t form
- Oxygenated & deoxygenated blood mixes in ventricle & gets pumped into both aorta & pulmonary trunk - body doesn’t receive fully oxygenated blood
Describe the transposition of the great vessels
- Aorticopulmonary septum forms but does not spiral causing Aorta & Pulmonary artery to be switched in position “transposed”
- RV connected to aorta & LV connected to pulmonary trunk (instead of the other way around)
Why is the transposition of great vessels a cyanotic defect?
Deoxygenated blood carried to body via aorta
What does the transposition of great vessels result in?
- Results in two unconnected parallel circulations instead of two circulations in series
- Pulmonary & systemic circulations are separated
How does the body still receive blood in the transposition of great vessels?
VSD, ASD & patent ductus arteriosus allow blood to mix so some oxygenated blood is pumped to rest of body
How does stenosis lead to pulmonary valve?
- One/both semilunar valves don’t develop properly & narrow when baby is born
- LV/RV hypertrophy as heart is generating more force to push blood through stenosed valve
- Hypertrophy can lead to heart failure
Describe how the resting membrane potential of cardiac cells is generated
Selective permeability of the cell membrane to K+ & the concentration gradient for K+ that exists across the cell membrane – approx. 90 mV
K+ ATPase sets up concentration gradient of ions
